1. Field of Invention
The present invention relates to structural reinforcement in general and in particular to reinforcing adjacent wood product structural members to each other.
2. Description of Related Art
In the field of construction, it is often desirable to make a structure as strong as possible. The strength of a building is desirable for the purposes of load bearing ability as well as resistance to outside loads such as earthquakes, wind and other environmental loading.
Building construction typically includes a plurality of elongate members connected each other to form walls, ceilings, floor and the like. In the case of walls, such elongate wall members are often referred to as studs while in ceilings and roofs, they may be referred to as joist.
One difficulty that exists is the tendency of relatively long structural members to loose strength and rigidity as their length increases. This is often required for floor and ceiling joists so as to provide larger rooms unobstructed by supporting walls and columns. Such long joists may commonly be subject to torsional buckling failure. Another difficulty that exists with floor joists is when they are exposed to dynamic environmental loads such as earthquakes, strong winds and the like. Under such loads, the floor joists may rotate axially along their length so as to lay flat instead of upright. The resulting horizontal and vertical deflection of the entire load above such a floor may contribute to an entire building failing or collapsing.
Conventional methods of reinforcing structural members has not been adequate to resolve the above difficulties. Previous attempts have tried to locate bridges or blocks between adjacent joists to distribute point loads located near a single joist to adjacent joists so as to distribute the load between more than one joist. Bridging involves locating a pair of crossed diagonal wooden members between adjacent joist whereas blocking typically includes locating a shortened length of the joist member transversely between the joists. Such attempts have not adequately solved the above difficulties. In particular, blocking or bridging is only able to act as a compressive member between the joists and will have a very limited ability to prevent the joists from moving away from each other.
When the joist members are subjected to torsional loading, the blocking members on one side of the joist are subjected to opposite loads. For example, when a torsional load is applied to the joist along the longitudinal axis of the structural member, the blocking member abutting one side of the top chord of the joist is subjected to a primarily compressive load, and the blocking member abutting opposite side of the top chord is subject to a tensile load. Similarly, for the same torsional load, the bottom chord on the same side of that joist will also be subjected to a tensile load. The compressive load may be conveyed efficiently to the blocking member abutting the top chord through the contacting surfaces of the blocking and the joist chord. However the tensile load on both blocking member on the opposite side of the top chord and on the bottom blocking member is born entirely by the fastening device used. Therefore unless such fasteners are specifically designed to bear tensile loads under repeated loading cycles, this is likely to lead to cause premature failure of the structure when such fasteners, such as a nail or a screw pulls out. Due to the inability of bridging and blocking to effectively handle loads in tension, such reinforcing will not significantly assist in the reinforcing of a structure under cyclical environmental loads such as earthquakes, winds and the like.